1. Technical Field
The present invention is concerned with multilayer films which are used in the production of semiconductor circuits and systems. The films may become a permanent part of the circuit or system; or, they may be used as masks which are removed during processing, so that they do not become part of the final circuit or system.
The present invention is particularly concerned with a method of producing multilayer polymeric films wherein at least one of the layers is etch-resistant.
2. Background Art
In the manufacture of semiconductor chips and systems, including packaging, multilayer films are used as insulators, semiconductors, and conductors. In the production of patterned devices, multilayer films are often used to achieve pattern transfer.
An example of the pattern transfer application is the use of multilayer films as masks during processing steps. Frequently the multilayer masking films are polymeric, due to ease of use and the relatively low cost of such materials. Depending on the pattern to be transferred, the multilayer mask may be comprised of several different polymeric materials, each material to accomplish a specific task. For example, a substrate to which a mask is to be applied may exhibit a multitude of geometries, necessitating the use of a planarizing layer prior to the layer of masking which is patterned (the imaging layer), in order to provide accuracy during patterning. Once the imaging layer has been patterned, it is necessary to transfer the pattern through the planarizing layer to the substrate. A current trend in the semiconductor industry is to use dry etching techniques to transfer the pattern through the planarizing layer. This is because conventional wet processes, which utilize solvent to transfer the pattern in the imaging layer through the planarizing layer, do not provide the anisotropic removal mechanism considered necessary to achieve optimal dimensional control within the parameters of today's systems.
Examples of dry-developable multilayer patterned films (resists) are provided in U.S. Pat. Nos. 4,426,247 to Tamamura et al., 4,433,044 to Meyer et al., 4,357,369 to Kilichowski et al., and 4,430,153 to Gleason et al. In all of the above patents, one of the resist layers comprises a silicon-containing polymer. The silicon-containing layer is imaged and developed into a pattern. Subsequently, the patterned layer of resist is exposed to an oxygen plasma or to reactive ion etching; this causes the formation of silicon oxides in the patterned layer, which protect underlaying polymeric layers and permit transfer of the pattern through the underlying polymeric layers.
Recently, processes have been developed which permit selective conversion of portions of a non-silicon-containing resist layer to a silicon-containing, etch-resistant form. The resist layer is imaged but not developed, and the latent image within the layer is reacted with an organometallic reagent to incorporate an oxide-forming metal such as silicon into the image. The latent image is then dry developable, and the etch-resistant images, as well as underlying planarizing layers, can then be dry etched using an oxygen plasma to simultaneously develop and transfer the pattern through to the substrate below.
Examples of this latter method of obtaining dry-developable multilayer resists are described in U.S. Pat. No. 4,552,833 to Ito et al., and in U.S. patent application Ser. No. 679,527 (assigned to the assignee of the present invention). The disclosures of U.S. Pat. No. 4,552,833 and U.S. patent application are incorporated herein by reference.
However, the methods of creating dry-developable multilayer resists described in the two referencies above provide a negative tone pattern, and many practitioners within the semiconductor industry prefer to use a positive tone pattern. In addition, the two methods described present problems on application to novolak resist materials of the type most commonly used in semiconductor industry lithography.